Cleaning sheet for typewriter type



April 1962 R. A. HUNDER ETAL 3,029,457

CLEANING SHEET FOR TYPEWRITER TYPE Filed July 30, 1959 Layer of erecff/ock fibers 400%0' W/W? norma/(y-fac/(y A va raps Q40 4 flu/voae 5/ 7x1500025 5UCHHOL rz ater 3,629,457 Patented Apr. 1 7, 1962 3,029,457SHEET FOR TYPEWRITER TYPE Ray A. Huntler, White Bear Lake, and TheodoreBuchholtz, Maplewood, Minn, assignors to Minnesota Mining andManufacturing Company, St. Paul, Minn, a corporation of Delaware FiledJuly 30, 1959, Ser. No. 830,601 3 Claims. (Cl. 15-210) CLEANING Thisinvention relates to a flexible cleaning sheet adapted to be inserted ina typewriter for cleaning the type when struck against the sheet; theink ribbon having been shifted so as not to interfere. The product insheets or tapes of suitable size can be similarly employed for cleaningthe type of other typing machines, such as printing calculating machinesa A flexible nonsticky cleaning sheet or tape is provided, having anonsticky ink-receptive and ink-retentive flocked face side, soconstructed that the sheet or tape can be directly fed into a typingmachine with the flocked face side exposed to impact of the type,without sticking to the machine, and be employed to eifectively cleanthe type by the mere striking of type thereagainst. The flocked faceside is comprised of a fuzzy layer of erect spacedapart short-staplerayon (or equivalent) flock fibers that are coated with an ink-receptiveadhesive which, although it is normally tacky, does not render the sheetor tape sticky to the touch on ordinary handling. This latter featureresults from the extreme thinness of the adhesive coating on the fibersand is obtained even when the adhesive is of a type employed inaggressively tacky pressure-sensitive adhesive tapes. I

The cleaning expedients heretofore commonly used by typists have beeninefficient, inconvenient and messy. It has been diflicult to clean typewithout ending up with soiled fingers. Painstaking elfort has beenrequired to thoroughly clean all of the type-particularly letters andnumerals having small loops-so that a uniform sharp imprinting orstencil cutting performance of the machine would be obtainable. In sometyping devices the type is not conveniently accessible to cleaning byconventional methods.

The use of solvents, as in using a brush that has been dipped insolvent, is hazardous and is objected to by manufacturers of electrictypewriters owing to risk of harming the mechanism into which thedirtied solvent may be splattered or dripped. Cleaning putties areineflicient and become fouled with repeated use so as to dirty thefingers. The use of pins or picks or the like for cleaning out loopedtype is tedious and may result in specks of dirty ink getting into themechanism or onto the fingers, and may result in scratching or otherwisedamaging the type characters. Dry brushing causes flicking of inkparticles and is ineffective because of the tenacity with whichaccumulated ink deposits cling in the type recesses. The labor cost ofmaintaining an ofiice typewriter in really good writing conditionthroughout a years time, by use of prior expedients, has beenconsiderable.

The present cleaning sheet may be conveniently provided in common lettersize (e.g., 8% x 11") for typewriter usage. It has a flexibility andthickness comparable to a set of paper sheets interleaved with copyingtissues as commonly inserted into a typewriter. It is not sticky andsheets can be kept in a drawer without sticking to each other or toother objects.

To clean the type of a typewriter, the typist merely feeds the cleaningsheet into the machine in the usual manner and types upon it, the ribbonhaving been shifted out of the way so that the type will directly strikeagainst the surface of the sheet. Each key is depressed one or moretimes depending upon how dirty the particular type character is, themovement of the carriage automatically bringing a fresh portion of thesheet into position for each type impact, and the paper being advancedafter each line is typed. Removed ink is retained in the body of thesheet and firmly held, and provides a tell-tale mark, after each typeimpact. When no appreciable mark is left, the typist knows thateffectively complete cleaning of the particular type character has beenachieved. In the case of an electric typewriter, it is a convenientprocedure for the typist to run her finger down each row of keys untilno marking of the sheet is observed.

A typewriter can be easily and continually maintained in good typingcondition by cleaning it in this way at the beginning of each Work day,in which case only a minute or two is required, the type never having achance to become badly fouled.

Upon completion of each cleaning job, the sheet is removed and is keptfor further use unless it has been used up. The utilized portion can beeasily cut off with a pair of scissors and discarded. A transverselyperforated sheet can be provided so that successive strips of the sheetcan be torn off as they are used from time to time. Removal of the usedportion of the sheet after a cleaning operation is desirable when badlyfouled type have been cleaned and have left heavy deposits of inkmaterial. But there is no need of so doing when relatively clean typehave been cleaned as the ink deposits will be light and will be retainedby the sheet so as to avoid smudging. One letter size sheet suflices fora number of cleaning operations, depending on how dirty the type areeach time the sheet is used.

The present cleaning sheet comprises a flexible backing (paper or film)carrying a flexible binder coating on the face side which bonds theinner tips of a fuzzy layer of erect spaced-apart flock fibers (such asshort-staple viscose-rayon flock fibers). This flocked side of the sheetis coated with a normally-tacky ink-receptive rubbery adhesive so as tosize or thinly coat the fibers, Without filling the interstices, leavingvoids larger than the fibers between the fibers and providing a porousfibrous layer. The tacky erect adhesive-coated free fibers are ofsufiicient length, stilfness and pliancy to reach and scrape the baseand side areas of the type characters impacted against the sheet, sothat ink deposits can be loosened and removed from all portions and thetype will be effectively cleaned.

The tacky ink-receptive adhesive coating thereon enables the fiockfibers to more readily remove, and also to retain, the ink when a typecharacter is struck against the sheet. The etficiency and convenienceare vastly greater than is obtainable in the absence thereof. The tackyfibers are bent down by the type impact and cohere together so that mostof the removed ink becomes absorbed into the fibrous layer below theplane of the outer tips of the surrounding fibers. This aids inminimizing subsequent smudging. The adhesive is highly cohesive andleaves no residue upon the type or on parts of the typewriter that itcontacts. Rolling of the cleaning sheet through the typewriter alsoserves to clean the platen pressure rollers which bear against the sizedflock surface, and which are normally inaccessible to cleaning and arenot cleaned by typists. A water-soluble or .markedly oleophobic type ofadhesive would not be compatible with the oily ink and hence would notbe ink-receptive and would not be suitable for present usage.

Although the fiber-sizing adhesive may be of the kind used inaggressively-tacky pressure-sensitive adhesive tapes, the fuzzy flockedstructure and the extreme thinness of the adhesive coating on thefibers, prevents the sheet from having a tacky feel when handled andfrom sticking to the back of another sheet, or to other objects, that itmay contact. It would not be apparent on ordi-,

nary scrutiny and handling that such an adhesive coating is employed.However, if a forefinger is firmly pressed against the flocked face ofthe sheet so as to mash down the fibers, a tacky feel can be readilydetected.

A fuzzy layer of short-staple flock fibers, as employed in the presentproduct, is quite different from a bristly or brush-like layer formed ofbristles. The present cleaning sheet does not perform the function of abrush but operates on a disparate principle.

The structure of this cleaning sheet is illustrated in the accompanyingdiagrammatic drawing of a greatly enlarged section.

A flexible backing 1 (such as a sheet of dense paper), preferablyprovided on the back side with an antislip backsize coating 2, carrieson its face side a flexible binder coating 3 which securely holds alayer 4 of erect spacedapart flock fibers whose inner tips are embeddedtherein and which are thinly coated with a normally-tacky inkreceptiverubbery adhesive. This fiber-sizing adhesive covers the exposed surfacesof the fibers (and also the underlying binder coating) without cloggingup the interstices between the fibers, thereby providing a porous layerof adherent free fibers.

The adhesive coating operation may result in some of the fibers beingadhered to contiguous fibers to form bundles or clumps of two or a fewfibers, as indicated in the drawing, but these function in substantiallythe same manner as do the individually coated free fibers and it is notnecessary to avoid formation thereof in the manufacture of the product.Nor is it necessary that the coating operation result in completecoating of all fibers from tip to base. It is not necessary that thefibers stand perfectly straight and erect. An approximation of the idealis satisfactorily useful.

Example A dense wet-strength kraft paper web, having a basis weight ofabout 150 lbs. per thousand square yards (about 80 kgs. per thousandsquare meters) and a caliper thickness of approximately 5 mils (0.13mm), is given a thin sizing coating on the back of synthetic rubber(such as a butadicne-styrene copolymer) to provide an antislip backsurface. A coating of colloidal silica in a binder may alternatively beemployed to roughen the back surface and provide an antislip surface.The purpose of this backsize is to provide the back surface of theproduct with an antislip characteristic that facilitates rolling thesheet into and through a typewriter. A backsize may be selected whichalso serves to clean the platen roll as the sheet is rolled through thetypewriter.

This backing sheet web is continuously coated on the face side with abinder resin solution or dispersion. While this coating is still softand tacky, the web is passed through a flocking machine whereshort-staple viscoserayon flock fibers are flocked into the surface inthe desired density so as to embed the inner ends of the erect fibers inthe binder coating. The web is then passed through an oven to dry orcure the binder coating and set the fibers. As flocking machines andprocedures are well known in the textile industry, a detaileddescription unnecessary.

The flocked web is then passed through a coating machine adapted toapply a solution of the adhesive to the fibrous face. Any suitablecoater may be used, such as a roll coater, knife coater or air knife. Adilute solution of adhesive is applied in a limited amount such that thecoating thereof breaks up and thinly coats the individual fibers, anddrains down to cover the underlying binder coating. The web is thenpassed through a drying oven, resulting in the type of productpreviously described. The dried web can then be cut into sheets ofdesired size ready for packaging and sale.

Examples of binder compositions for providing the flexible. bindercoating are aqueous dispersions of plasticized thermosettingurea-formaldehyde resins, and of polyvinyl acetate. When a paper backingis coated with an aqueous binder composition, a type of paper whichincludes a wet-strength sizing should be employed so that it will haveadequate strength and freedom from distortion during the coating,flocking and drying operations. The coating weight is adjusted so thatthe flock will be firmly bonded. Only a thin dried coating is needed toanchor the tips of the fibers, thus permitting of a product sheet whichis thin enough and flexible enough to be inserted into a typewriterwithout requiring a leader.

The viscose-rayon flock should have a high enough denier value(indicative of the fiber diameter) to provide adequate stiffness. Thedenier value should be at least 1.5 and a value of S to 10 is preferred.The flock fibers should have adequate length for eflicient type cleaningaction, but should not be so long as to make the sheet too thick foreasy passage into and through the typewriter carriage. A length of 30 to40 mils is desirable and a length of about 35 mils (0.9 mm.) ispreferred in making cleaning sheets for conventional typewriters inwhich the type characters have a height of 25 mils. The density of theflock (number of fibers per unit area) is also related to the typecleaning, and the ink removing and retaining, eficiency of the sheet.The fibers should not be packed together but should be spaced-apart toprovide a fuzzy porous layer. This factor is most easily controlledduring manufacture by adjustment of the flock coating weight. It isdesirable that this weight be in the range of about 125 to 200 lbs. perthousand square yards of sheeting (about 70 to kgs. per thousand squaremeters), preferably about 160 pounds per thousand square yards (about 90kgs. per thousand square meters), when using flock fibers of about 5denier size and 35 mils length.

The preferred fiber-sizing adhesives are pressure-sensitive adhesivessuch as are well-known in the adhesive tape art. In normal dry form theyare aggressively tacky to the touch. They are rubbery (viscoelastic) andhighly cohesive. The usual rubber-resin pressure-sensitive adhesives asused in adhesive tapes provide water-insoluble oleophilic coatings. Theyare compounded from natural rubbery or a rubbery synthetic polymer(elastomer) and an admixed compatible tackifier resin; or formed of arubbery type of polymer which is inherently aggressively tacky. Forpresent usage, it is preferred to employ a pressure-sensitive adhesivethat is stable to long-continued exposure to air and light, since theadhesive coated fibers of the cleaning sheet are accessible to theatmosphere, thereby avoiding loss of tack for at least several months.Adhesives utilizing air and light stable polymers are thereforepreferable-such as adhesives embodying polyisobutylene, polyacrylate orpolyvinyl ether polymers.

A preferred example of an adhesive coating solution applied by rollcoating, has the following formulation (parts by weight):

Parts Rubbery polyisobutylene (such as Vlstanex B) 100 Low molecularweight tacky polyisobutylene (such as Vistac A70) 70 Pure hydrocarbonterpene tackifier resin (such as Piccolyte S85) 45 Rosin ester tackifierresin (such as Hercolyn") 30 Di-tert.-amyl hydroquinone (antioxidant)(such as Santovar A) l Heptane (volatile solvent) 1800 The driedadhesive coating on the fibers is only a thin size coating. Thus in thepreferred construction described above (using pounds of flock perthousand square yards), the adhesive may have a dry weight of about 100pounds per thousand square yards of sheeting (about 55 kgs. per thousandsquare meters); this includes both the coating on the flock and thecoating on the underlying binder layer.

It is not essential that the fiber-sizing adhesive have the aggressivedegree of tackiness characteristic of pressure-sensitive tape adhesives.For example, a rubberybase cleaning putty that is slightly tacky to thetouch in normal dry form, may be utilized to provide the fibersizingadhesive, being applied to the flocked sheet as a dilute dispersion inwater. Such cleaning putty compositions are well-known and may comprisea mixtur of synthetic rubber, factice, oil and inorganic filler, forinstance. Use may be made of rubbery polymers, and of rubber andtackifler resin blends, which have a mild degree of tackiness that isless than that of pressure-sensitive tape adhesives. These need only besufliciently tacky so that the sized flock fibers are renderedink-receptive.

Simple experimentation will enable one to arrive at various satisfactorycombinations. Although viscoserayon flock fibers are preferred and arereadily and eco' nomically available, other equivalent fibers can beused,

such as nylon flock and polyester flock. Equivalent natural fibers mayalso be used.

The present cleaning sheets and tapes in appropriate sizes can be usedfor other purposes for which suitable, such as for cleaning suede shoesand felt hats by lightly rubbing.

We claim:

1. A flexible nonsticky cleaning sheet or tape of the characterdescribed, having a nonsticky ink-retentive flocked face side, soconstructed that the sheet or tape can be directly fed into a typingmachine with the flocked face side exposed to impact of the type,without sticking to the machine, and be employed to eflectively cleanthe type by th mere striking of type thereagainst, comprising a thinflexible backing flocked on the face side with a fuzzy layer of erectspaced-apart short-staple flexible flock fibers of type-cleaning lengthwhose inner tips are bonded to the backing, the flock fibers having asizing coating thereon of a normally-tacky ink-receptive rubberyadhesive which is so extremely thin that voids larger than the fibersare provided between free fibers, and such that the sheet or tape is'notrendered sticky and the presence of the adhesive is not apparent onordinary handling not involving a mashing down of the fibers, theflexible adhesive-coated free fibers having a degree of stiflness thatpermits both of cleaning type and of bending down and cohering togetherwhen struck by type.

2. A flexible nonsticky cleaning sheet or tape of the characterdescribed, having a nonsticky ink-retentive flocked face side, soconstructed that the sheet or tape can be directly fed into a typingmachine with the flocked face side exposed to impact of the type,without sticking to the machine, and be employed to effectively cleanthe type by the mere striking of type thereagainst, comprising a thinflexible backing flocked on the face side with a fuzzy layer of erectspaced-apart short-staple flexible flock fibers of type-cleaning lengthwhose inner tips are bonded to the backing, the flock fibers having asizing coating thereon of a normally and aggressively tacky inkreceptiverubbery pressure-sensitive adhesive that is stable to long-continuedexposure to light and air and which is so extremely thin that voidslarger than the fibers are provided between free fibers, and such thatthe sheet or tape is not rendered sticky and the presence of theadhesive is not apparent on ordinary handling not involving a mashingdown of the fibers, the flexible adhesive-coated free fibers having adegree of stiflness that permits both of cleaning type and of bendingdown and cohering together when struck by type.

3. A cleaning sheet according to claim 2, which is of at least about 8/2 x ll" size and wherein said flock fibers are viscose-rayon fibershaving a denier value of about 5 to 10 and a length of about 30 to 40mils.

References Cited in the file of this patent UNITED STATES PATENTS

1. A FLEXIBLE NONSTICKY CLEANING SHEET OR TAPE OF THE CHARACTERSESCRIBED, HAVING A NONSTICKY INK-RENTENTIVE FLOCKED FACE SIDE, SOCONSTRUCTED THAT THE SHEET OR TAPE CAN BE DIRECTLY FED INTO A TYPINGMACHINE WITH THE FLOCKED FACE SIDE EXPOSED TO IMPACT OF THE TYPE,WITHOUT STICKING TO THE MACHINE, AND BE EMPLOYED TO EFFECTIVELY CLEANTHE TYPE BY THE MERE STRIKING OF TYPE THEREAGAINST, COMPRISING A THINFLEXIBLE BACKING FLOCKED ON THE FACE SIDE WITH A FUZZY LAYER OF ERECTSPACED-APART SHORT-STAPLE FLEXIBLE FLOCK FIBERS OF TYPE-CLEANING LENGTHWHOSE INNER TIPS ARE BONDED TO THE BACKING, THE FLOCK FIBRES HAVING ASIZING COATING THEREON, OF A NORMALLY-TACKY INK-RECEPTIVE RUBBERYADHESIVE WHICH IS SO EXTERMELY THIN THAT VOIDS LARGER THAN THE FIBERSARE PROVIDED BETWEEN FREE VOIDS FIBRES, AND SUCH THAT THE SHEET OR TAPEIS NOT RENDERED STICKY AND THE PRESENCE OF THE ADHESIVE IS NOT APPARENTON ORDINARY HANDLING NOT INVOLVING A MASHING DOWN OF THE FIBERS, THEFLEXIBLE ADHESIVE-COATED FREE HAVING A DEGREE OF STIFFNESS THAT PERMITSBOTH OF CLEANING TYPE AND OF BENDING DOWN AND COHERING TOGETHER WHENSTRUCK BY TYPE.